The cystic fibrosis transmembrane regulator (CFTR), the product of the gene mutated in patients with cystic fibrosis, has adapted the ABC transporter structural motif to form a tightly regulated anion channel at the apical surface of many epithelia. Use of the term assembly of a functional ion channel implies the coming together of subunits or at least smaller not-yet functional components of the active whole. In fact, on the basis of current knowledge only the CFTR polypeptide itself is required to form an ATP- and protein kinase A-dependent low-conductance chloride channel of the type present in the apical membrane of many epithelial cells. CFTR displays the typical organization (IM-ABC)2 and carries a characteristic hydrophilic R-domain that separates IM1-ABC1 from IM2-ABC2.
Jiyao W et al.(2023). "The conserved domain database in 2023.",